Abstract [en]

An organogelator was produced and identified from a dynamic imine system, resolved and amplified by selective gelation. The formation of the organogel was monitored in situ by H-1 NMR, showing the existence of multiple reversible reactions operating simultaneously, and the redistribution of the involved species during gelation. The formed organogelator proved effective with a range of organic solvents, including DMSO, toluene, and longer, linear alcohols.

Zhang, Yang

Abstract [en]

This thesis is divided into three parts, revolving around the developments of dynamic systems utilized in dynamic kinetic resolution (DKR) and constitutional dynamic chemistry (CDC).

The first section gives an introduction to constitutional dynamics, the core concept of this thesis. Constitutional dynamics can be tuned through reversible interactions. Then, the basic principles of constitutional dynamics in DKR and CDC are discussed, along with their applications.

The second section explores the asymmetric synthesis of oxazolidinone derivatives using lipase catalysis through kinetic resolution (KR) and dynamic kinetic resolution. In the first example, synthetic protocol to enantioenriched 5-phenyloxazolidin-2-ones is described, where a kinetically controlled carbamation is followed by lipase-catalyzed cyclization. In contrast to the 5-substituted species, the synthesis of 3-phenyloxazolidin-2-one derivatives could be achieved through lipase-catalyzed cascade O- and N- alkoxycarbonylations in one pot. Furthermore, this KR system could be coupled to a ruthenium-catalyzed racemization process of 1,2-aminoalcohols, thus providing an efficient DKR methodology for asymmetric transformations.

The third section focuses on dynamic systems built through reversible covalent reactions. In the first example, a selective gelation process is described, and employed to resolve dynamic imine systems consisting of gelator candidates. In the second example, reversible reactions with aldehyde enamines are presented, including enamine formation and exchange reactions. In particular, Bi(III) and Sc(III) were discovered to accelerate the enamine exchange reactions by 50-400 times, in which the equilibria could be reached within hours. The last example describes reversible nitroaldol reactions in aqueous media, where rapid and efficient equilibration was identified for selected structures in neutral phosphate buffer.